An interlaboratory comparison of aerosol inorganic ion measurements by ion chromatography : Implications for aerosol pH estimate

Water-soluble inorganic ions such as ammonium, nitrate and sulfate are major components of fine aerosols in the atmosphere and are widely used in the estimation of aerosol acidity. However, different experimental practices and instrumentation may lead to uncertainties in ion concentrations. Here, an intercomparison experiment was conducted in 10 different laboratories (labs) to investigate the consistency of inorganic ion concentrations and resultant aerosol acidity estimates using the same set of aerosol filter samples. The results mostly exhibited good agreement for major ions Cl-, SO2-4, NO-3, NHC4 and KC. However, F-, Mg2C and Ca2C were observed with more variations across the different labs. The Aerosol Chemical Speciation Monitor (ACSM) data of nonrefractory SO2-4, NO-3 and NHC4 generally correlated very well with the filter-analysis-based data in our study, but the absolute concentrations differ by up to 42 %. Cl-from the two methods are correlated, but the concentration differ by more than a factor of 3. The analyses of certified reference materials (CRMs) generally showed a good detection accuracy (DA) of all ions in all the labs, the majority of which ranged between 90 % and 110 %. The DA was also used to correct the ion concentrations to showcase the importance of using CRMs for calibration check and quality control. Better agreements were found for Cl-, SO2-4, NO-3, NHC4 and KC across the labs after their concentrations were corrected with DA; the coefficient of variation (CV) of Cl-, SO2-4, NO-3, NHC4 and KC decreased by 1.7 %, 3.4 %, 3.4 %, 1.2 % and 2.6 %, respectively, after DA correction. We found that the ratio of anion to cation equivalent concentrations (AE/CE) and ion balance (anions-cations) are not good indicators for aerosol acidity estimates, as the results in different labs did not agree well with each other. In situ aerosol pH calculated from the ISORROPIA II thermodynamic equilibrium model with measured ion and ammonia concentrations showed a similar trend and good agreement across the 10 labs. Our results indicate that although there are important uncertainties in aerosol ion concentration measurements, the estimated aerosol pH from the ISORROPIA II model is more consistent

Numerical Simulation of Rock Burst of Circular Roadway Based on RFPA Software

Based on RFPA software, the numerical simulation of rock burst in circular roadway is carried out under different horizontal stresses. The paper studies the distribution of stress field, the crack propagation and acoustic emission characteristics in the process of rock burst. The results show that the stress moves and the concentration of compressive stress appears on left and right sides of roadway after excavation of the roadway, and tensile stress zone appears at the top and bottom of the roadway. The shear fracture on the roadway’s left and right sides is more serious. The larger the horizontal stress is, the earlier the energy releases and the higher the total energy is

Numerical Simulation of Rock Burst of Circular Roadway Based on RFPA Software

Based on RFPA software, the numerical simulation of rock burst in circular roadway is carried out under different horizontal stresses. The paper studies the distribution of stress field, the crack propagation and acoustic emission characteristics in the process of rock burst. The results show that the stress moves and the concentration of compressive stress appears on left and right sides of roadway after excavation of the roadway, and tensile stress zone appears at the top and bottom of the roadway. The shear fracture on the roadway’s left and right sides is more serious. The larger the horizontal stress is, the earlier the energy releases and the higher the total energy is

Study on Mine Rock Disaster Based on Acoustic Emission Technology

Study the effect of water on the acoustic emission quiet period before the destruction of rock based on the uniaxial loading experiment of acoustic emission of drying, natural and saturated basalt. The results show that the drying, natural and saturated basalt have AE quiet period before rupture. The load level of AE quiet period quiet period increase and shorter duration, and quiet period recognition is more difficult.AE quiet period, the AE event rate maintain per 10, but AE energy rate is not calm and characterized by accelerated release, and the release rate decreases with the increasing of water content. Due to full water characteristics of the actual mining basalt and the complexity of its fracture, the dominant frequency the AE rate of mutational characteristics and the AE event rate calm characteristic can be combined used to obtain information. The rate of mutation phenomenon before AE quiet period can be used as early warning information of saturated basalt rupture, and AE quiet period can be used as precursory information of saturated basalt rupture

Study on Mine Rock Disaster Based on Acoustic Emission Technology

Study the effect of water on the acoustic emission quiet period before the destruction of rock based on the uniaxial loading experiment of acoustic emission of drying, natural and saturated basalt. The results show that the drying, natural and saturated basalt have AE quiet period before rupture. The load level of AE quiet period quiet period increase and shorter duration, and quiet period recognition is more difficult.AE quiet period, the AE event rate maintain per 10, but AE energy rate is not calm and characterized by accelerated release, and the release rate decreases with the increasing of water content. Due to full water characteristics of the actual mining basalt and the complexity of its fracture, the dominant frequency the AE rate of mutational characteristics and the AE event rate calm characteristic can be combined used to obtain information. The rate of mutation phenomenon before AE quiet period can be used as early warning information of saturated basalt rupture, and AE quiet period can be used as precursory information of saturated basalt rupture

Experimental Investigation of the Formation of Rockburst Pits in Circular Tunnel Based on CT Scanning

The rockburst simulation experiments of granite samples with a circular hole under biaxial loading were conducted, and the samples were scanned by computed tomography (CT) at the end of experiment. Through a series of CT images, the failure characteristics of the circular hole wall were analysed to determine the types of rockburst pits, and the detailed formation process of different types of rockburst pits was studied in combination with the crack characteristics around them. The experimental results indicate that there are mainly two types of rockburst pits, namely, pan-shaped and V-shaped, which can occur symmetrically or asymmetrically on the left and right sidewall of the circular hole. The formation of rockburst pits is related to the cracks parallel and perpendicular to the principal stress. Cracks parallel to the principal stress can determine the depth of the rockburst pit and affect the type of the rockburst pit, and cracks perpendicular to the principal stress determine the width of the rockburst pit. There is a correlation between the formation process of pan and V-shaped rockburst pits. During the formation of a V-shaped rockburst pit, several rockbursts occur, and each rockburst forms a pan-shaped rockburst pit. In the process of developing from the tunnel wall to the deep rock, the width of the pan-shaped rockburst pit gradually decreases and a V-shaped rockburst with a stepped upper and lower boundary is formed

A method of production profile quick prediction based on typical curves: A case study of the Upper Shale large multi-layered sandstone reservoir, Rumaila Oilfield, Iraq

Combined the advantage of reservoir simulation and conventional reservoir engineering methods, the paper proposes a quick method for production performance prediction, which is based on type curves generated from reservoir simulations of sector model. Fine reservoir simulation is conducted based on the fine geological sector model of the large sandstone reservoir, and type curves of different reservoir type under different development options are generated. Then based on results of reservoir type classification for all layers, well productivity and injectivity evaluation, production profile of the whole field can be predicted. This new method can reflect the impact of reservoir heterogeneity and development option change on reservoir performance. Take a large multi-layered sandstone reservoir Upper Shale reservoir in Rumaila Oilfield for example to illustrate the workflow. The comparison between results of fine reservoir simulation and that of the new method validate reliability of the new method, and the new method consume much shorter time. Key words: Iraq, Rumaila Oilfield, type curve, production profile, quick prediction, sector model, numerical simulatio

Experimental Investigations into the Effects of Lithology on Acoustic Emission

In order to study how lithology affects acoustic emissions (AE), a series of tunnel rock burst simulation experiments, monitored by acoustic emission instruments, were conducted on granite, marble and basalt. By analyzing the characteristic parameters, this study found that AE events occur more frequently during the rock burst process on granite and basalt. Marble remains dormant until 75% of the loading time before the peak, at which point, cracks develop rapidly and AE events dramatically increase. During the rock burst process, the AE energy release demonstrates that low energy is released in the incubation phase and robust energy is released during the later phase. Before the rock burst occurs, increased in the heterogeneity index Cv values of the AE event are subject to lithology. The Cv values of granite and basalt have an increase of about 0.2-0.4, while marble shows an increase of 1.0-1.2. The heterogeneity index Cv value of an AE event is in line with the rock burst process

The Mechanical and Fracturing of Rockburst in Tunnel and Its Acoustic Emission Characteristics

The phenomenon of acoustic emission (AE) is associated with rock failure and rock fracturing. In order to investigate the influence of tectonic stress on rockburst in tunnel, a biaxial loading experiment system was used in this study. The excavation operation is undertaken at the center of samples to monitor the tunnel forming process in situ, and the different horizontal stresses can be studied by using the AE monitoring technique. The dynamical fracturing process of the tunnel model was summarized, and the timing parameters of AE signals in rockburst stages were obtained. The curves of AE energy and cumulative AE energy with time show a “step-like” rising trend before the occurrence of rockburst. The evolution of macro- and mesocracks is captured, and the mechanical conditions for a “V-shaped” rockburst pit are derived. As the horizontal stress increases, the effect of excavation unloading becomes more pronounced, and the damage caused by the rockburst intensifies. In the early stage of rockburst evolution, the fracturing type follows a model of tensile-shear mix model. A positive relationship between the ratio of shear fracturing type and the horizontal stress can be noted when the rock is about to burst, and the high intensity and the high energy released of from the rock-fracturing event have become evident. Thus, the results indicate that one should focus on monitoring both sides of the surrounding rock of the tunnel so as to extract the characteristics of the process of tunnel in tunnel. The applications of biaxial loading system and during an excavation operation provide a useful tool to simulate the rock burst in tunnel at an engineering site